1. Field of the Invention
The present invention relates to a belt stretching mechanism. This invention may be employed to stretch the alternator V-belt in an internal combustion engine to a specified tension.
2. Description of the Prior Art
With the conventional alternator in an internal combustion engine, as illustrated in FIG. 10, the rotation of crank pulley 1 is transmitted to alternator pulley 3 through V-belt 5 wound around alternator pulley 3 of alternator 2 and water pump pulley 4. For alternator 2 and the water pump to function normally, V-belt 5 should be maintained at an adequate tension.
As enlarged in FIGS. 11 and 12, the top of conventional alternator 2 is supported by bracket 6. The bottom of alternator 2 is fastened by alternator stay 7, which extends downward from alternator 2. Stay 7 cooperates with slider 8 and adjust bar 9, which is fixed to the engine cylinder block, to holder alternator 2 in place. The tension of V-belt 5 is adjusted by loosing lock bolt 10 and therefore slider 8 which has been fastened together with alternator stay 7 to adjust bar 9 and changing the support angle of alternator 2 by rotating adjust bolt 11 which is screw-engaged with slider 8.
However, in this tension adjustment of V-belt 5, axis 12 of adjust bolt 11 is off-set from axis 13 of lock bolt 10. Therefore, when V-belt 5 is stretched by turning adjust bolt 11 in the tightening direction, the off-set causes a moment on slider 8 and a bending moment on adjust bolt 11. As a result, slider 8 inclines and the head of adjust bolt 11 inclines with respect to the bolt hole of adjust bar 9 through which adjust bolt 11 extends. The inclination of slider 8 and the head of adjust bolt 11 makes turning of adjust bolt 11 unsmooth and may cause such problems that V-belt 5 can not be stretched to a specified tension and that rigidity of adjust bolt 11 has to be increased to prevent bending of adjust bolt 11.